Arrow Kinetic Energy Calculator

Kinetic energy in foot pounds is arrow weight in grains times speed in feet per second squared, divided by 450240. A 400 grain arrow at 280 fps gives (400 x 280 x 280) / 450240 = 69.65 ft-lb.

Common guidelines suggest about 25 ft-lb or more for small game, 40 ft-lb or more for deer, and 60 to 65 ft-lb or more for larger animals such as elk. Check your local regulations and shot placement.

Momentum is arrow weight in grains times speed, divided by 225218, in slug feet per second. Heavier arrows carry more momentum at the same energy, which many hunters link to deeper penetration.

Speed counts more because energy rises with the square of velocity, while weight is only linear. That said, a heavier arrow shot from the same bow loses less speed and often retains energy better downrange.

Use the measured speed from a chronograph, ideally a few yards in front of the bow. Advertised IBO speeds are measured under fixed conditions and usually run faster than a hunting setup.